Field of the Invention
The present invention relates to an image processing apparatus capable of conveying and reading a document, a method for controlling the image processing apparatus, and a storage medium.
Description of the Related Art
An image processing apparatus, such as a copying machine or a facsimile apparatus, is equipped with an image reading device. Further, among various image reading devices, there is an image reading device that is equipped with an automatic document feeder (ADF).
In many cases, the image processing apparatus has functions each requiring detecting a document size before starting a document image reading operation. The function requiring detecting the document size before starting the image reading operation is, for example, an automatic paper selection function or an automatic magnification selection function.
The automatic paper selection function is a function of automatically selecting a paper having an appropriate size based on a document size, a designated magnification, and required image rotation processing. Further, the automatic magnification selection function is a function of calculating an image magnification required to enlarge or reduce a read document image according to a designated paper size and automatically setting the calculated image magnification. The above-mentioned functions (i.e., the automatic paper selection function and the automatic magnification selection function) can be realized by a controller provided in the image processing apparatus.
Further, as a document image reading mode using the ADF, a same width mixed document reading mode or a different width mixed document reading mode becomes important to cause the image processing apparatus to read a document bundle composed of a plurality of document sheets that are different in size. Even when the image processing apparatus performs a document image reading operation according to either the same width or the different width mixed document reading mode, a user requires that the reading efficiency is maintained at a high level.
When the image processing apparatus processes documents without setting the same width or the different width mixed document reading mode, the image processing apparatus regards the documents as being identical in size. Therefore, a fixed document size can be identified based on document width information obtainable when the document is set on a document tray of the ADF or document length information obtainable when the document is initially conveyed in the feeding direction.
As one type of the ADF, the apparatus can be configured to have a large scale to provide a conveying path that is sufficiently long. According to the ADF having such a large-scale configuration, it is feasible to determine the document width information and the document length information before a leading edge of each document reaches a document reading position. On the other hand, in many cases, the large-scale ADF is heavy and expensive because the entire configuration of the apparatus tends to be excessively large.
On the other hand, as another type of the ADF, the apparatus can be configured to have a document conveying path that is comparatively short. For example, the ADF can be designed to set a conveying path length (i.e., the length from a paper feeding position of a document placed on the document tray to the document reading position) to be shorter than the length of an A4-size document (i.e., document width 297 mm×document length 210 mm) that is generally used by many users. Such an ADF is advantageous in that the entire configuration is compact. In a case where the above-mentioned compact ADF performs an ordinary reading operation for reading a document bundle composed of a plurality of document sheets that are identical in document size, the ADF determines the length of the documents set on the document tray, by using a sensor provided in the document tray to identify the document size based on the document width information and the document length information.
However, the above-mentioned ADF has the following problem because the document conveying path is comparatively short. A control differentiated from the ordinary reading operation is required in a case where the ADF realizes the automatic paper selection function and the automatic magnification selection function when the ADF reads each sheet of a document bundle composed of a plurality of document sheets that are mutually different in document size in the different width mixed document reading mode in which the ADF reads each document while automatically identifying the size thereof. According to the above-mentioned ADF, both of the width and the length of each sheet are unknown in a state where only a target document is set on the document tray. Therefore, identifying the document size before starting a document reading operation is unfeasible.
Therefore, the above-mentioned ADF identifies the size of each document by detecting the width of the document or the length of the document in the document conveying direction while the document is conveyed along a reversing conveying path (i.e., a circulative path) that is used for reversing the document when the ADF reads images formed on both sides of the document. Even in the same width mixed document reading mode, a similar problem arises because the length of each sheet in the document conveying direction is unknown in a state where only a target document is set on the document tray.
Accordingly, when the ADF performs a reading operation according to the same width or the different width mixed document reading mode, the ADF performs hollow reversing processing in such a way as to convey a target document along a circulative path to identify the document size for each page. Therefore, the same width/the different width mixed document reading mode is inferior to the ordinary (or standard) size document reading mode in that the reading efficiency deteriorates.
Further, as a technique capable of solving the above-mentioned reduction in reading efficiency, among ADFs, there is an ADF configured to predict a document size so as to avoid performing the above-mentioned hollow reversing processing as much as possible.
As discussed in Japanese Patent Application Laid-Open No. 2006-074124, in a case where the document size is unknown in the same width/the different width mixed document reading mode, it is conventionally known to extract a plurality of candidates of the document size based on a detected width and then determine one of the candidates as a provisional document size. However, in a case where neither the same width nor the different width mixed document reading mode is set, if the documents being stacked are mixed in size or if something other than a target document to be read (e.g., other document bundle) is placed on a sensor provided on the document tray, the document size may be erroneously detected and a miscopy may occur.
For example, as mentioned above, if the document size is erroneously detected as A3 even though the document being actually set on the ADF is A4, the result obtainable through a reading operation is an A3 size image. In this case, the obtained A3 size image is constituted by a document image positioned on one side (corresponding to an A4 size area) and a blank image positioned on the other side (corresponding to the remaining A4 size area). For example, if the blank image portion of the above-mentioned A3 size image is printed on an A4 paper, the print result will be regarded as a miscopy. On the other hand, according to the mixed document reading mode, the above-mentioned miscopy does not occur because the size of each document is determined after the document is pulled in the ADF.
Further, as discussed in Japanese Patent Application Laid-Open No. 2009-67559, a technique capable of solving the above-mentioned problem is conventionally known. More specifically, in a case where the mixed document reading mode is not set, it is conventionally known to prevent the occurrence of miscopy by interrupting a document conveying operation when documents being conveyed are mutually different in width.
The technique discussed in Japanese Patent Application Laid-Open No. 2006-074124 requires a user to perform a mixed document designation setting. Further, if the document size prediction is failed in the document size detection, it is required to perform a reading operation again through the document hollow rotation processing. It takes a significant time to complete the document reading operation including the hollow rotation processing. Further, the document size determination is feasible only after the document is pulled in the ADF. Therefore, the timing to start the latter processing (e.g., print) is delayed. As a result, the reading efficiency deteriorates significantly.
Further, according to the technique discussed in Japanese Patent Application Laid-Open No. 2009-67559, the reading efficiency deteriorates similarly because interrupting the document reading operation is necessary to prevent the occurrence of miscopy.